The document describes an NDIR gas sensing circuit designed by Rishav Pandey at CSIR-CEERI under the guidance of Dr. Ravindra Kumar Jha. The circuit uses components like an IR light source, optical filters, thermopile and thermistor IR detectors, op amps, a low noise amplifier, analog microcontroller, and voltage regulator. The PCB is designed to interface with an Arduino board. It uses AD8629 op amps to amplify sensor signals and an ADuCM360 microcontroller to control the lamp voltage and read the ADC outputs to analyze gas concentrations.